Escalators and moving walkways are subject to high, changing levels of load by strongly fluctuating numbers of users and have long operating times of 10 to 18 hours per day. In buildings with public traffic such as, for example airports, railway stations or underground stations, escalators and moving walkways can even be in permanent use around the clock. Accordingly, the moved parts of these items of transport equipment are exposed to high levels of wear and therefore have to be intensively and thoroughly maintained. Link chains of the plate belt or of the step belt as well as the chainwheels arranged in the deflecting regions are parts with high levels of wear (wear parts) which have to be periodically replaced. A chainwheel serves for deflection of the runs of the link chain in dependence on running direction of the step belt or plate belt from a forward run to a return run or from the return run to the forward run. In addition, the link chain can be driven by a chainwheel. Guide rollers are usually fastened to the link chains in order to guide the plate belt or step belt at least in the forward run by means of guide rails arranged between the deflecting regions and to provide support against gravitational force.
Link chains with guide rollers of this category are disclosed in, for example, U.S. Pat. Nos. 4,883,160 A, 4,930,622 A and GB 491 301 A.
Escalators and moving walkways of flat construction have been increasingly developed in recent years. These have many advantages in terms of constructional engineering for customers. For example, in the case of escalators with low constructional heights it is possible to dispense with a pit in the floor or only a pit with a small depth is still necessary. Escalators with smaller constructional heights can be installed more easily in existing buildings, since the installation space available from the removed, old escalator is usually sufficient. In a given case the support structure of the escalator to be replaced can be left and the new escalator inserted into the old support structure or framework.
In order to build an escalator or moving walkway of flat construction it is necessary, in particular, to reduce the diameter of the conveying chainwheel and the deflecting chainwheel. This leads to a substantial deflection of the chain links or chain link straps of the link chain in the region of the deflecting chainwheel or conveying chainwheel. Moreover, for the same pitch, but with decreasing pitch circle diameter of the chainwheel and thus with increasing tooth number, the so-called polygon effect increases, i.e. a non-uniform movement of the step belt or plate belt. Various measures for elimination of polygon effect are disclosed in, for example, EP 1 876 135 B1.
These measures enable use of long chain link straps or chain links together with small deflecting chainwheels and conveying chainwheels without a polygon effect occurring or with this being barely detectable at least by the users. However, the lengthy articulation point spacings of the link chain additionally increase the deflection angle at the articulation points and for a predetermined pitch circle diameter at the circumference of the chainwheel less teeth are in engagement with the link chain, as a consequence of which the area pressure at the guide rollers and thus wear thereof is substantially higher than in the case of chainwheels with the same pitch and larger pitch circle diameter. Guide rollers of steel, which are more wear-resistant than plastics material guide rollers, are in fact also mentioned in EP 1 876 135 B1, but these steel rollers cause a considerable amount of operational noise on the guide rails.